Groundwheels for aircraft

ABSTRACT

An aircraft wheel drive unit has a fluid-pressure-operated motor housed within the wheel and two planetary gear stages housed in a gearbox outboard of the motor, the final drive being transmitted from a ring gear of the second gear stage, which is inboard of the first stage, to the wheel through an output drive quill coupled, through a disc-type clutch if desired, to a flanged final drive member bolted to the wheel. The gear box and the motor are supported from the wheel by a bearing assembly within the flanged final drive member and surrounding the inner end of the gearbox. The motor has a torque coupling to the end of the non-rotary wheel axle to prevent rotation of the motor stator and gearbox. Structural integrity is given to the wheel-supporting assembly by providing a structural connection from an extension of the motor body to a spider secured within the gearbox through a non-rotary planet gear cage of the second gear stage.

United States Patent 1' Cameron-Johnson [11] 3,711,043 Jan. 16, 1973[54] GROUNDWHEELS FOR AIRCRAFT [75] Inventor: Alan Cameron-Johnson, St.Albans,

England [22] Filed: Sept. 21, 1970 [211 App]. No.: 73,871.

[30] Foreign Application Priority Data Primary ExaminerTrygve M. BlixAssistant Examiner-Paul E. Sauberer Attorney-Dowell and Doweli [57]ABSTRACT An aircraft wheel drive unit has a fluid-pressureoperated motorhoused within' the wheel and two planetary gear stages housed in agearbox outboard of the motor, the final drive being transmitted from aring gear of the second gear stage, which is inboard of the first stage,to the wheel through an output drive quill coupled, through a disc-typeclutch if desired, to

Oct. 13, 1969 Great Britain ..50,2l6/69 a flanged final drive memberbolted to the wheel. The gear box and the motor are supported from thewheel [52] US. Cl ..244/50, 180/55 by a bearing assembly within theflanged final drive [51] Int. Cl ..B64c 25/00 member and urrounding theinner end of the gear- [58] Field Of Search "ISO/5 5; 244/50, 103 R boxTh motor has a torque coupling to the end of the non-rotary wheel axleto prevent rotation of the 1' References cued motor stator and gearbox.Structural integrity is given UNITED STATES PATENTS to thewheel-supporting assembly by providing a structural connection from anextension of the motor body 2,869,662 KOUP to a spider secured withinthe gearbox through a nonrotary planet gear cage of the second gearstage.

11 Claims, 3 Drawing Figures i|E| 4 27 26 25 26b 9 Ma i. 26a 75-11mm- Ei I f' '-=.'.l{ 22 'iq iiinnui'| '?'-%.'IIJ ==-'L 2a igimq lhJ" .gfi-A:29

4/ illl PATENTED JAN 1 6 I973 3.711 043 SHEET 2 BF 3 WM 2 W- I lnvenlorv @M l mam! PATENTEDJAH 16 I975 SHEET 3 [IF 3 GROUNDWHEELS FOR AIRCRAFTThis invention relates to groundwheels for aircraft, more particularlyself-powered groundwheels.

The concept of a civil VTOL aircraft landing area from which tractorsand other servicing vehicles are excluded because of the trafficdensity, gives rise to the need for a self-propelling capability on thepart of the aircraft themselves. A further restriction imposed by thelimited size of the landing area and the density of traffic, is the needto avoid the use of main thrust engines for maneuvering on the ground.

It is therefore an object of the invention to accept both theselimitations by providing propulsion of an aircraft through itsgroundwheels.

According to the present invention, an aircraft groundwheel drive unitcomprises a fluid-pressure operated motor within the wheel and aplanetary gear train axially outward of the motor through which themotor drive is transmitted to a flanged annular final driving membersurrounding the inner end of the gear box and secured to the wheel, thegear box structure and motor body having a torque connection to thenonrotary axle of the wheel to prevent rotation but being supported bythe rotary wheel in a bearing assembly within said flanged final drivingmember.

In the preferred construction, the planetary gear train comprises firstand second planetary gear stages, and the second stage is inward of thefirst and has a non-rotary planet gear cage that is designed to form astructural element of the gearbox and unites the gear box structure tothe motor body.

In the case of a strictly VTOL aircraft that will not perform landingsat any significant forward speed, the drive motor may be in permanentdriving connection with the wheel. But for an aircraft intended foroccasional conventional landings a clutch to disconnect the drive may beincorporated between the gear train and said flanged final drivingmember.

Two constructions according to the invention are shown in detail, by wayof example, in the accompanying drawings, in which:

FIG. 1 shows the first construction in longitudinal section,

FIG. 2 is a corresponding view of the second construction, and

FIG. 3 is a view in section on the line 3-3 of FIG. 2.

FIG. lshows a hollow three-part double-tired aircraft ground wheel 11mounted for rotation around a non-rotary undercarriage axle 12. A swashplate type hydraulic motor 13 is disposed concentrically in a cavity 14within the wheel beyond the end of the axle and has its stator orcasing13a coupled by a splined flange member 15 and a co-operating splinedsleeve 16 to the end of the axle 12, the fluid lines to and from themotor 13 running inside the axle 12 to a supply and return system on theundercarriage leg. The motor output drive is delivered by a quill 17coaxial with the wheel which extends outward away from the axle 12 andhas at its outer end a pinion 18. From this pinion the drive istransmitted to the wheel 11 through a two-stage planetary gear assembly.

The pinion 18 constitutes the sun wheel of the first stage planetarygear 19 and is surrounded by three planet gears 21 mounted in a rotarycage 22. This cage is coupled at 23 to the sun wheel 24 of the secondplanetary stage which is carried by the cage 22 and located around thequill l7 inward of the first stage 19. The planet gears 21 of the firststage are in mesh with a surrounding ring gear 25 that is fixed to thenon-rotary housing 26 of the gear assembly. The gear housing 26 is intwo parts 26a, 26b held together by bolts 27. The part 26a constitutesan end cover and is fitted with an axial spigot 28 carrying a bearing 29for the gear cage 22. The part 26b constitutes the main body of the gearhousing and extends axially inwards to enclose the inner second stage ofplanetary gearing 20 and the outer end of the motor 13. The inner end 31of the gear housing part 26b is somewhat reduced in diameter and isreceived within a bearing assembly 30 carried in a sleeve 32 that lieswithin the outer end of the wheel 1 l. The sleeve 32 has a flange 33 atits outer end which is bolted to the end of the wheel 11 so that thewheel and the flanged sleeve 32 rotates as one.

The motor casing has an outward axial extension 34 which provides aseating at 35 for the planet gear cage 36 of the second planetary gearstage 20. This cage is non-rotary and carries three planet gears 37which mesh, on the one hand, with the sun wheel 24, and, on the otherhand, with a surrounding rotary ring gear 38. The cage 36 is secured tothe motor casing 13a by bolts 39, and it also has formed integrallythereon at its outward side a spider 40 with a peripheral flange 41 thatis secured to the gear housing 26 by the bolts 27.

The output drive from the planetary gear. assembly is taken from thering gear 38. A large diameter quill 42 coupled to this ring gearextends axially inward therefrom through an annular gap between themotor casing extension 34 and the inner end of the gear housing 26 andis free to rotate in bearing assemblies 43, 44 on the motor casing andgear housing, respectively. The inner end of the quill 42 has a splinedsleeve coupling at 45 to a flanged ring 46 the flange 47 of whichextends radially out past the inner end 31 of the gear housing 26 and isbolted to a flange 48 on the inner end of the flanged sleeve 32. Thus,the drive from the motor 13 is transmitted via the quill l7 and the twoplanetary gear stages 19, 20, the quill 42 and flanged ring 46 and theflanged sleeve 32 to the wheel 11.

A feature of this arrangement is that although the assembly of gear boxstructure and motor body is non-rotary it is not supported by thenon-rotary axle but instead in the bearing assembly 30 carried by therobust flanged rotary sleeve 32 bolted to the wheel and merely has aspline coupling to the axle through the motor body to prevent rotation.Since the only connection to the axle is by way of the splines 49 on themotor body and the loose sleeve 16, the whole assembly can be withdrawnfrom the wheel upon unbolting the external flange 33. This constructionis made possible by the use of the non-rotary cage 36 of the secondplanetary gear stage 20 as a structural element of the gearbox,connecting the gearbox proper to the hydraulic motor casing 13a. Thehydraulic connections within the axle are made before assembly of thedrive unit to the wheel, utilizing telescopic sliding joints betweenrigid pipes and a central manifold to give pull-out access to the pipeunions.

The arrangement in FIG. 1 is intended for a VTOL aircraft havingnegligible forward speed on landing and where the requirements are for apermanently connected drive with the ability to accelerate the aircraftup to a taxiing speed not exceeding, say, to mph. in a reasonably shorttime and to maintain headway against wind gusts and small gradients.Similar drive units are provided on all main undercarriage wheels andpreferably on the nose wheels also since the weight distribution of aVTOL aircraft may give high nose loads and therefore good nose wheeltraction. Each individual drive unit is of comparatively small diameter,i.e. less than the diameter of the wheel rim, and operates withreasonably high efficiency in both forward drive and reverse. A furtheradvantage of the non-rotating gearbox arrangement is that, with thegearbox remaining in one attitude, the provision of filling andlevelling plugs for the gear lubricant presents no problem.

Since there is no disconnection between the gear trains and the wheel,the mechanism will not tolerate a suddenly applied forward speed andtheconsequent high accelerations and velocities within the unit. For thisreason, the design in FIG. 1 is restricted purely to vertical landingand take-off. This clearly imposes limitations, some of which will beunacceptable in certain instances. A landing with forward speed cannotbe performed without destruction of the transmission system, but sincethe wheel is too small, in any case, to accommodate a brake other thanfor parking, there is no provision for conventional landing. Towing bytractor is limited since the backpressure imposed by the open-circuitedhydraulic system could give a drag up to 15 percent of the drivingtractive effort.

FIGS. 2 and 3 show an arrangement generally similar to that of FIG. 1but enlarged and modified to accept conventional landings with forwardspeed. The small tires, running at high deflection in FIG. 1, and thewheel diameters, have to be significantly increased for a conventionallanding. The wheel brake 50 now required fits the wheel which has almostdouble the rim diameter. The enlarged size of wheel makes possible theinclusion of a hydraulically-applied clutch in the wheel drivetransmission unit. The associated wheel tires will have adequate loadcapacity and speed capability for up to 200 kts.,

The drive unit in FIGS. 2 and 3 is considerably smaller in diameter thanthe wheel rim 51 and largely contained within it. In this instance, theflange 33 whereby the final driving sleeve 32 is secured to the wheel isat the inner end of the sleeve, instead of the outer end as in FIG. 1,and is made small enough in diameter to permit the wheel rim 51 to bedetached from the wheel hub 52 without disconnection of the drive unit.The bearing assembly for the gear housing 26 is carried by the flangedsleeve 32 at its outer end.

The clutch 53 comprises an assembly of sliding clutch discs 54 carried,on the one hand, internally of the sleeve 32 intermediate its ends and,on the other hand, externally of an inward cylindrical extension 55 ofthe ring 46 that is coupled to the drive quill 42. The clutch is engagedby the pressing together of the clutch discs 54 between the flange 47 onthe ring 46 and a flange 56 on the inner end of a clutch-operatingsleeve 57. The clutch-operating sleeve is mounted for rotation on athrust bearing 58 which surrounds a further sleeve 59 that in turnsurrounds the axially-moving cylinder 60 of a clutch-actuating pistonand cylinder assembly.

The cylinder contains a non-moving annular piston 61 and a floatingpiston 64 arranged so that Whichever of two fluid pressure ports of themotor 13 receives pressure fluid, for either forward or reverse drive,the cylinder member 60 is urged to the left as viewed in the drawing.When the cylinder 60 moves to the left it carries with it the sleeve 59,and a flange or shoulder 62 at the inner end of the sleeve 59 exerts aleftward force on the bearing 58 and clutch-operating sleeve 57, throughthe intermediary of spring discs 63, to cause the clutch to engage.

The clutch is normally disengaged, and permits high speed taxiing of theaircraft without reverse-driving the gear train. Engagement of theclutch is, as stated, due to application of hydraulic pressure to eitherport of the motor, and occurs at low pressure (about 6% percent ofnormal motor pressure) to ensure engagement before the motor speeds up.The potentially high load due to full pressure, which would be excessivefor the structure and thrust bearing, is relieved by the suitablypreloaded disc springs 63.

Although emphasis has been laid on the VTOL case, it will be understoodthat the invention is not limited in application to this since there canbe an advantage in having self-propulsion on conventional aircraft,particularly large ones operating on icy taxi-ways. Under theseconditions, a tractor may not be able to obtain sufficient tractionbecause of its low relative weight, when most of the weight isconcentrated on the aircrafts main wheels. The second embodimentdescribed herein would then be applicable.

I claim:

1. An aircraft ground wheel and drive unit assembly comprising: a hollowground wheel mounted on a nonrotary undercarriage axle extendingcoaxially within said wheel, a fluid-pressure-operated rotary motorsituated coaxially within said hollow wheel and including a motor rotorand a non-rotary motor casing, a non-rotary gear box situated axiallyoutward of said wheel, a planetary gear train mounted within the gearbox, a driving connection coupling said motor rotor and said planetarygear train, a flanged rotary annular final driving member surroundingthe inner end of said gearbox and secured to said wheel, coupling meanswhereby said annular final driving member is driven by said planetarygear train, and a bearing assembly within said annular final drivingmember providing a mounting and support for said motor casing and saidgearbox while permitting said final driving member to rotate relativelythereto, said gearbox and said motor casing having a torque-transmittingconnection to said non-rotary axle to provide restraint againstrotation.

2. An assembly according to claim 1, wherein the planetary gear traincomprises first and second planetary gear stages, and the second stageis inward of the first and has a non-rotary planet gear cage that isdesigned to form a structural element of the gearbox and units the gearbox structure to the motor casing.

3. An assembly according to claim 2, wherein a clutch to disconnect thedrive is incorporated between the gear train and said flanged finaldriving member.

4. An assembly according to claim 3, wherein the motor is a hydraulicmotor disposed concentrically in a cavity within the wheel beyond theend of the axle and has its casing prevented from rotation by atorquetransmitting coupling between the casing and the axle end, thefluid lines to and from the motor being led inside the axle, and themotor output being delivered to the planetary gear train by a coaxialquill extending outward away from the axle.

5. An assembly according to claim 4, wherein the motor output quillcarries at its outer end a sun pinion of the first planetary gear stagewhich meshes with planet gears on a rotary planet gear cage that drivesa sun pinion of the second gear stage surrounding the quill inward ofthe first, the planet gears on the rotary planet gear cage also being inmesh with a surrounding ring gear fixed within the gearbox.

6. An assembly according to claim 5, wherein the non-rotary planet gearcage of the second planetary gear stage is carried jointly by, on theinner side, an extension of the motor casing and, on the outer side, aradially-extending spider secured to the gearbox wall, and the outputdrive of the gearbox is provided by an output ring gear surrounding andin mesh with the planet gears on the non-rotary planet gear cage and anoutput drive quill which rotates with said output ring gear and extendsinward coaxially with the motor casing extension which it surrounds.

7. An assembly according to claim 6, wherein said flanged final drivingmember has a flange at its outer end secured to the wheel and extendsinward into the wheel around and beyond a reduced inner end portion ofthe gearbox, the bearing assembly supporting the gearbox and motor beingdisposed around said reduced inner end portion of the gearbox, and thedrive to the wheel is transmitted from said gearbox output drive quillto the inner-end of said flanged final driving member by means of aflanged sleeve coupled to the quill and extending inward coaxiallywithin the gearbox inner end portion and around the motor casing.

8. An assembly according to claim 3, wherein the flanged final driving,member has a flange at its inner end secured to the wheel, said bearingassembly supporting the gearbox and motor is disposed at or near itsouter end, and the clutch to disconnect the drive is disposed withinsaid final driving member.

9. An assembly according to claim 6, wherein the clutch comprises discsor plates keyed for rotation with the final driving member, furtherco-operating discs or plates keyed for rotation with a sleeve membercoupled to said gearbox output drive quill, and a fluid-pressureoperatedpiston-and-cylinder assembly arranged to engage the clutch discswhenever fluid pressure is admitted to the drive motor.

10. An assembly according to claim 9, wherein thefluid-pressure-operated clutch assembly comprises an annular cylindersurrounding the motor, with two pistons working therein in anarrangement such that the clutch is engaged irrespective of whetherpressure fluid is admitted to the motor for forward or reverse drive.

11. An assembly according to claim 9, wherein the clutch-engaging effortis transmitted to the clutch discs through a preloaded spring assemblywhich prevents the application of a high load due to the full motorfluid pressure.

1. An aircraft ground wheel and drive unit assembly comprising: a hollowground wheel mounted on a non-rotary undercarriage axle extendingcoaxially within said wheel, a fluid-pressure-operated rotary motorsituated coaxially within said hollow wheel and including a motor rotorand a non-rotary motor casing, a nonrotary gear box situated axiallyoutward of said wheel, a planetary gear train mounted within the gearbox, a driving connection coupling said motor rotor and said planetarygear train, a flanged rotary annular final driving member surroundingthe inner end of said gearbox and secured to said wheel, coupling meanswhereby said annular final driving member is driven by said planetarygear train, and a bearing assembly within said annular final drivingmember providing a mounting and support for said motor casing and saidgearbox while permitting said final driving member to rotate relativelythereto, said gearbox and said motor casing having a torque-transmittingconnection to said non-rotary axle to provide restraint againstrotation.
 2. An assembly according to claim 1, wherein the planetarygear train comprises first and second planetary gear stages, and thesecond stage is inward of the first and has a non-rotary planet gearcage that is designed to form a structural element of the gearbox andunits the gear box structure to the motor casing.
 3. An assemblyaccording to claim 2, wherein a clutch to disconnect the drive isincorporated between the gear train and said flanged final drivingmember.
 4. An assembly according to claim 3, wherein the motor is ahydraulic motor disposed concentrically in a cavity within the wheelbeyond the end of the axle and has its casing prevented from rotation bya torque-transmitting coupling between the casing and the axle end, thefluid lines to and from the motor being led inside the axle, and themotor output being delivered to the planetary gear train by a coaxialquill extending outward away from the axle.
 5. An assembly according toclaim 4, wherein the motor output quill carries at its outer end a sunpinion of the first planetary gear stage which meshes with planet gearson a rotary planet gear cage that drives a sun pinion of the second gearstage surrounding the quill inward of the first, the planet gears on therotary planet gear cage also being in mesh with a surrounding ring gearfixed within the gearbox.
 6. An assembly according to claim 5, whereinthe non-rotary planet gear cage of the second planetary gear stage iscarried jointly by, on the inner side, an extension of the motor casingand, on the outer side, a radially-extending spider secured to thegearbox wall, and the output drive of the gearbox is provided by anoutput ring gear surrounding and in mesh with the planet gears on thenon-rotary planet gear cage and an output drive quill which rotates withsaid output ring gear and extends inward coaxially with the motor casingextension which it surrounds.
 7. An assembly according to claim 6,wherein said flanged final driving member has a flange at its outer endsecured to the wheel and extends inward into the wheel around and beyonda reduced inner end portion of the gearbox, the bearing assemblysupporting the gearbox and motor being disposed around said reducedinner end portion of the gearbox, and the drive to the wheel istransmitted from said gearbox output drive quill to the inner end ofsaid flanged final driving member by means of a flanged sleeve coupledto the quill and extending inward coaxially within the gearbox inner endportion and around the motor casing.
 8. An assembly according to claim3, wherein the flanged final driving, member has a flange at its innerend secured to the wheel, said bearing assembly supporting the gearboxand motor is disposed at or near its outer end, and the clutch todisconnect the drive is disposed within said final driving member.
 9. Anassembly according to claim 6, wherein the clutch comprises discs orplates keyed for rotation with the final driving member, furtherco-operating discs or plates keyed for rotation with a sleeve membercoupled to said gearbox output drive quill, and afluid-pressure-operated piston-and-cylinder assembly arranged to engagethe clutch discs whenever fluid pressure is admitted to the drive motor.10. An assembly according to claim 9, wherein thefluid-pressure-operated clutch assembly comprises an annular cylindersurrounding the motor, with two pistons working therein in anarrangement such that the clutch is engaged irrespective of whetherpressure fluid is admitted to the motor for forward or reverse drive.11. An assembly according to claim 9, wherein the clutch-engaging effortis transmitted to the clutch discs through a preloaded spring assemblywhich prevents the application of a high load due to the full motorfluid pressure.